*
For all RCF focusers you must specify whether you want a flat or
curved base.
For curved bases, you need to specify the radius. If you
don't, you will get the standard size radius. Please
specify your selection by one of the two methods listed here:

METHOD 1
Select one of the options below to add your desired specs to the
shopping cart.

METHOD
2
Place a note in the shopping cart Comments area specifying
"Flat Base" or "Curved Base" and the
appropriate radius for the curved base.
(Diameter = 2 x Radius)

NOTE

When
using a laser collimator, keep in mind that there will be slight deviations in the laser
beam when moving the drawtube through the full length of travel. This deviation is
not noticeable visually, is only a small fraction of the amount present with a normal
rack-and-pinion focuser and is completely eliminated with the higher quality of
the EV focusers.

Due to the design of this focuser, the knobs
are at a 90-degree orientation from most, placing the drive shaft perpendicular to the
optical tube when using a curved base.

*
For all RCF focusers you must specify whether you want a flat or
curved base.
For curved bases, you need to specify the radius. If you
don't, you will get the standard size radius. Please
specify your selection by one of the two methods listed here:

METHOD 1
Select one of the options below to add your desired specs to the
shopping cart.

METHOD
2
Place a note in the shopping cart Comments area specifying
"Flat Base" or "Curved Base" and the
appropriate radius for the curved base.
(Diameter = 2 x Radius)

NOTE

When using a laser collimator,
keep in mind that there will be slight deviations in the laser beam when moving
the drawtube through the full length of travel. This deviation is not
noticeable visually, is only a small fraction of the amount present with a
normal rack-and-pinion focuser and is completely eliminated with the higher
quality of the EV focusers.

Due to the design of this focuser, the knobs
are at a 90-degree orientation from most, placing the drive shaft perpendicular to the
optical tube when using a curved base.

All RCF focusers can be purchased with either a flat base
or curved base. (Specify RCF model and "flat" or "curved"
base.)
The base plate is removable. The curved base on a 1.25" RCF-mini focuser has a standard radius of
3.75 inches (7.5" diameter) or an optional radius of 6 inches (12"
diameter). The 2" RCF has a standard radius of 10 inches (20" diameter)
or an optional radius of 5 inches (10" diameter).

Purchased as a separate
item, Part Number RCFBASE
An option when purchasing a focuser, Part Number N/A (See
"Method 1" Below)

*
For all RCF focusers you must specify whether you want a flat or
curved base.
For curved bases, you need to specify the radius. If you
don't, you will get the standard size radius. Please
specify your selection by one of the two methods listed here:

METHOD 1
Select one of the options below to add your desired specs to the
shopping cart.

METHOD
2
Place a note in the shopping cart Comments area specifying
"Flat Base" or "Curved Base" and the
appropriate radius for the curved base.
(Diameter = 2 x Radius)

RCF-mini1 focusers
come standard with a 3" length drawtube. This
option is for upgrading the drawtube length to
4.6" at the time of purchase. (A 2.5" drawtube length option
is available for the 1.25" RCF-mini1 focuser at no
additional charge.)

NOTE

The 4.6" length drawtube was
designed specifically for the Meade Starfinder
telescope. When replacing the Meade focuser with an RCF-mini1 focuser you can
use the standard 3" drawtube and an extension tube
or upgrade to the 4.6" drawtube. The extension tube option is best if
you plan on doing prime-focus photography (see the NGF
FAQ information).

The 4.6" drawtube for the 2" RCF-1 is no longer available. For the 2"
focuser replacement we recommend converting to an EV focuser

What is a Reverse
Crayford Focuser (aka Monorail)?

The Reverse Crayford Focuser (RCF) is a
light-weight, low-profile focuser with a new revolutionary design  JMI's low-cost,
high-quality answer to plastic focusers. In the reverse Crayford design,
the drive-shaft pressure is applied to a bar which "pulls" the
drawtube against its supporting bearings as apposed to directly
"pushing" the drawtube as seen in the normal Crayford
design. This design gives zero
image shift and zero backlash as with our EV
focusers. (U.S. Patent No. 6,297,917)

The motor, gear box and
drive train of every RCF motorized focuser is warranted by JMI Telescopes (Jim's Mobile, Inc.) to be free from defects in
material and workmanship for a period of five years from the date of original
purchase. JMI will repair or replace a part found to be defective, provided the
defective part is returned to JMI freight prepaid with proof of purchase.

What is
the Crayford Design?

The Crayford Eyepiece
Mount (CEM) was invented by John Wall. The Crayford name comes from the Crayford Manor House Astronomical Society
(UK) to
which he belongs. The Crayford design
uses high pressure on a metal drive shaft pressing against a metal drawtube
which is held by bearings on the opposing side. This direct
surface-to-surface drive mechanism eliminates backlash and shifting of the
drawtube as seen in other designs such as the rack-and-pinion focuser and
allows for very fine adjustments.

JMI
recognized the benefits of this design and was the first company to bring
it to the amateur market in a commercial product.
Mr. Wall, who chose not to patent his idea, continues to design and build
Crayford Focusers.

Customer
Comments

"I
only wish I had bought two [RCFs]." (P. G.)

"The RCF-mini1 focuser
is great. There was very little trouble fitting it onto my small
scope. Works great! ... Where is the deviation when
collimating? I have none, but that's good." (G. G.)

"Just a quick thank you
for the prompt and excellent service in delivering my latest JMI purchase,
an RCF focuser kit. JMI is proving now, more than ever, to be a real
leader in amateur astronomy. Thanks again. (R. M.)

"Many
thanks to you. The order arrived in very good time, is assembled
(and wowed a number of friends with the high quality parts and design) and
is to be installed in my dob... Congratulations on an excellently
made product." (F. H.)

"I just wanted to
thank you people for producing an excellent low-cost focuser. I purchased a Monorail
focuser a few weeks ago and I am impressed with the quality of the design. I am a
quality control manager of a machine shop in Texas and have seen a lot of mechanical
products and know that this focuser is an excellent quality focuser. I recommend
that anyone who needs a high quality focuser at an affordable price should purchase one of
yours." (R. N.)

"Received my
replacement part and the new invoice today. Thanks. As always, it's a pleasure
dealing with some of the best 'good guys' in the astro business!"
(R. M.)

"After a long and
exasperating search, I have not been able to find a better deal for this type of
focuser. It appears that JMI puts great emphasis in the quality, function and
reasonable price of their instruments. I truly look forward to receiving my order
and seeing for myself what the rave is all about." (M. D.)

"The whole
amateur community owes companies like yours a very great deal; uncompromising quality at
the cutting edge is what has driven this hobby forward so amazingly in the last twenty
years and where our entire future lies." (J. K.)

Frequently Asked Questions
(FAQ)

Q.

What are the
differences between the NGF and RCF focusers?

A.

The RCF focusers are
based on a new revolutionary reverse Crayford design (U.S. Patent No.
6,297,917). This new
design allows us to produce light weight metal focusers that are price competitive with
plastic versions. Another difference is the ability to change out the base of the
focuser by removing two screws which makes it easy to change between a flat base and a
curved base. The bases are made from formed aluminum rather than machined aluminum.
One more difference is the orientation of the knobs. On NGF focusers with a
curved base, the drive shaft is normally parallel with the optical tube. The design
of the RCF focuser places the drive shaft perpendicular to the optical tube when using a
curved base.

Q.

Can I add
a Motor to my RCF focuser at a later date?

A.

Yes, the
Motor attaches very easily. A gear slides onto the drive shaft and is secured with a
setscrew and the motor unit attaches to the drive block with two screws.
See Motor for
JMI RCF Focusers in our JMI Online Store.